assertion  retraction  graph  subject    predicate        object    datatype    annotation
1          0           graph  DOID:277   rdfs:subClassOf  DOID:780  _IRI        
1          0           graph  DOID:780   oio:id           DOID:780  xsd:string  
1          0           graph  DOID:2021  rdfs:subClassOf  DOID:780  _IRI